When you don't fully trust the locks on the hotel room door or when other means of securing a door fail, you can repurpose a dining fork to secure the door in a pinch.
This hack doesn't require a fork that's too strong or thick — a thin and long stainless one will do. Start by breaking the fork, completely severing its head from the handle.
Then, bend the fork so that the first quarter-inch is at a 90-degree angle. Open the door and place the forkhead inside the door latch so the bent tines are hanging onto it.
Now, shut the door, ensuring the forkhead is sticking out. Take the handle and slip it through the middle space of the fork tines until it passes underneath the door handle.
The fork against the latch and the fork handle against the foot will work as a jam, preventing anyone from opening the door from the other end, provided the door only opens inward.